Power-driven storage systems are used in many applications. One of these applications involves the storage of articles on an endless loop conveyor. Typically, each storage location on the conveyor is marked with a unique number.
To store an article, a human operator moves the conveyor by means of switches controlling the direction of movement of the conveyor. When an empty location is in front of the operator, the operator stops the conveyor. The operator puts the article in the empty location. The number of the location where the article is stored on the conveyor is noted along with the article identification in order to expedite retrieval of the article at a later time.
To retrieve the article, the operator looks at the notes, locates the note containing information on the desired article, and manually operates the conveyor to cause it to move to the location where the article is stored. This requires the operator to watch the location numbers as the conveyor moves, and to stop the conveyor when the desired article storage location is in front of the operator. The operator can then remove the desired article from the conveyor. This type of operation is typical of motor-driven conveyors having only right/left switches to control the conveyor.
An improvement on this technique is to automate the conveyor movement so that the operator simply enters the desired location number into a controller. The controller causes the conveyor to move using the shortest path to the desired location, and then stops the conveyor when the desired location is at the pickup location where the operator is standing. Systems using this technique are available, but suffer from several types of problems.
In one system the conveyor position sensor is mounted directly to the conveyor drive motor shaft. The motor is connected through a drive belt to a gearbox which in turn drives the conveyor. Drive belt slippage in this embodiment results in loss of synchronization between the conveyor position sensor and the conveyor itself, requiring periodic resetting of the controller.
In another system the conveyor is required to be of a special type, having specially designed sensors that are only available from the conveyor manufacturer, thus preventing retrofit of a single type of controller on conveyors from multiple manufacturers.
A further improvement on conveyor controllers is to use a computer database to keep track of the location of stored articles. On storing an article, the selected storage location on the conveyor is stored in the database along with the article identification. Later retrieval is accomplished by the operator selecting the desired article in the database, whereupon the computer containing the database communicates the article's storage location to the controller. The controller then causes the conveyor to move to the article's storage location. In systems using this technique, multiple operators fetching articles off the same conveyor must keep track of who is currently fetching an article, so that when the conveyor automatically stops at an article, the proper operator can be alerted. Also, typical controllers of this type can only be operated from a keypad located at the controller, and have no provision for remote control via a connection to a computer Point-of-sale (POS) system.
An even further improvement on this technique is to display information concerning the article being retrieved on a display located at the controller. In this way one operator does not need to remain at the conveyor while it is moving to a desired location. When the conveyor stops at a storage location, information concerning the article stored there can be displayed. Any operator can then look on the display to determine what to do with the article at the storage location. For example, the display could indicate the name or identifier for the operator who is fetching that article, as well as the article identifier.
Another problem with existing designs is that they provide no capability for communicating the current conveyor location to a database to associate with the identification of a just-stored article. The existing designs all count on the operator accurately noting the location at which an article has been stored. Errors made by the operator in the article location notes requires time-consuming manual search of the conveyor for lost articles.
Still another problem with some existing designs is that they require setting of switches to calibrate the controller to the length of the conveyor (e.g. U.S. Pat. No. 4,484,288).